EXPLAIN输出列

列名 含义
id 该SELECT标识符
select_type 该SELECT类型
table 输出行表
partitions 匹配的分区
type 联接类型
possible_keys 可能的索引选择
key 实际选择的索引
key_len 所选键的长度
ref 与索引比较的列
rows 估计要检查的行
filtered 按表条件过滤的行百分比
Extra 附加信息

例子 - Full Table Scan - *

  • idx_firstname
  • idx_firstname_middlename
  • idx_firstname_middlename_lastname
  • idx_age
    1. select * FROM test_isolation.user;
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例子 - Full Index Scan - id

  • idx_firstname
  • idx_firstname_middlename
  • idx_firstname_middlename_lastname
  • idx_age
    1. select id FROM test_isolation.user;
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例子 - Full Index Scan - firstname

  • idx_firstname
  • idx_firstname_middlename
  • idx_firstname_middlename_lastname
  • idx_age
    1. select firstname FROM test_isolation.user;
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例子 - Full Index Scan - middlename

  • idx_firstname
  • idx_firstname_middlename
  • idx_firstname_middlename_lastname
  • idx_age
    1. select middlename FROM test_isolation.user;
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例子 - Full Index Scan - lastname

  • idx_firstname
  • idx_firstname_middlename
  • idx_firstname_middlename_lastname
  • idx_age
    1. select lastname FROM test_isolation.user;
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例子 - Full Index Scan - firstname,middlename

  • idx_firstname
  • idx_firstname_middlename
  • idx_firstname_middlename_lastname
  • idx_age
    1. select firstname,middlename FROM test_isolation.user;
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例子 - Full Index Scan - firstname,middlename,lastname

  • idx_firstname
  • idx_firstname_middlename
  • idx_firstname_middlename_lastname
  • idx_age
    1. select firstname,middlename,lastname FROM test_isolation.user;
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例子 - Full Table Scan - firstname,middlename,lastname,age

  • idx_firstname
  • idx_firstname_middlename
  • idx_firstname_middlename_lastname
  • idx_age
    1. select firstname,middlename,lastname,age FROM test_isolation.user;
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例子 - Full Table Scan - firstname,middlename,lastname,age,remark

  • idx_firstname
  • idx_firstname_middlename
  • idx_firstname_middlename_lastname
  • idx_age
    1. select firstname,middlename,lastname,age,remark FROM test_isolation.user;
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例子 - Full Index Scan - firstname,lastname

  • idx_firstname
  • idx_firstname_middlename
  • idx_firstname_middlename_lastname

  • idx_age

    1. select firstname,lastname FROM test_isolation.user;

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    例子 - Full Index Scan - middlename,lastname

  • idx_firstname

  • idx_firstname_middlename
  • idx_firstname_middlename_lastname

  • idx_age

    1. select middlename,lastname FROM test_isolation.user;

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    例子 - Full Index Scan - firstname,age

  • idx_firstname

  • idx_firstname_middlename
  • idx_firstname_middlename_lastname

  • idx_age

    1. select firstname,age FROM test_isolation.user;

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    例子 - Full Table Scan - firstname,remark

  • idx_firstname

  • idx_firstname_middlename
  • idx_firstname_middlename_lastname
  • idx_age
    1. select firstname,remark FROM test_isolation.user;
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